From the state of the art, within the framework of an automatic start-stop mechanism, a known process is to automatically shut down internal combustion engines of motor vehicles in the event of a standstill, for the reduction of fuel consumption and emissions, upon the fulfillment of certain conditions, for example at a traffic light, and to restart such engines when necessary, for example upon actuating the drive pedal or the gear selector of the gearbox.
Thereby, with automatic transmissions, upon an engine start from an engine stop of the automatic start-stop mechanism, it is usually the case that several shifting elements are actuated in a short period of time. Thereby, with hydraulically actuated automatic transmissions, a certain amount of oil volumes must be deployed for the control of the shifting elements in this short period of time. Due to the time required for the necessary oil supply, the reaction time, i.e., the time until the start of the internal combustion engine, is extended, resulting in a loss of comfort.
In order to ensure the necessary oil supply required for the control of the automatic transmission, supplemental oil supply systems are generally used, which disadvantageously results in an increase in manufacturing costs and weight. For example, the transmission oil pump or a supplemental pump can be driven by an electric motor. In addition, an energy storage device in the form of an impulse storage device can be provided, whereas the energy storage device is designed as a spring piston accumulator, which is filled with oil during the operation of the internal combustion engine and stretches a spring that advances back the stored oil quantity into the transmission upon the restart of the internal combustion engine.
In order to minimize the additional costs for the supplemental oil supply systems and also reduce the reaction time, upon an engine start from an engine stop of the automatic start-stop mechanism, as little oil as possible made available by the supplemental oil supply systems should be necessary. Ideally, no supplemental oil supply systems should be required.
DE 10 2010 020 066 A1 shows a method for the operation of an automatic start-stop mechanism for a motor vehicle with an internal combustion engine and an automatic transmission having shifting elements for the adjustment of the gear steps, within the framework of which, upon the fulfillment of specifiable shut-off conditions for the internal combustion engine, a gear step is automatically engaged, which is higher than the first gear step and from which a downshift is possible in the first gear step without the actuation of a shifting element of the automatic transmission, for example through the opening of the valves, whereas the internal combustion engine is automatically switched off after engaging the higher gear step.
Thereby, upon the fulfillment of specifiable restarting conditions, the internal combustion engine is automatically restarted, whereas, immediately after the restart, the first gear step is automatically engaged, preferably by merely opening the valves.
Through the known method, an engine start from an engine stop of the automatic start-stop mechanism is to be carried out without supplemental oil supply systems.